By NICOLE WINFIELD and RACHEL ZOLL
PHILADELPHIA (AP) -- Pope Francis met with victims of child sexual abuse Sunday on the final day of his U.S. visit and promised to hold accountable those responsible for the scandal in the church, delivering a powerful warning to American bishops accused of covering up for pedophile priests instead of reporting them to police.
The pontiff disclosed the gesture of reconciliation at the start of a meeting with American bishops gathered in Philadelphia for a big rally on Catholic families.
But in a move that signaled a new effort by the church to redirect the discussion, the Vatican said not all five of the victims were abused by members of the clergy; some of the three women and two men had been victimized by family members or educators.
Francis praised the victims as "true heralds of mercy" who deserve the church's gratitude for their "essential contribution" toward establishing the truth. Saying sex abuse in the church can no longer be kept a secret, he promised to "zealously" protect young people and see that "all those responsible are held accountable."
The pope has agreed to create a new Vatican tribunal to prosecute bishops who failed to protect their flock by covering up for pedophile priests.
It was his second such meeting: Last summer he met at the Vatican with a group of victims of child-molesting priests.
But Francis and U.S. bishops have also argued that child molestation is a serious problem beyond the church, especially within families and in schools. The pope's meeting with victims abused by people other than priests underscored that point.
The Archdiocese of Philadelphia has been hit hard by the scandal and has been the subject of repeated grand jury investigations, including one that accused it keeping on assignment more than three dozen priests facing serious abuse accusations. A monsignor was found guilty of endangering children by not removing pedophile priests, becoming the first American church official convicted of such an offense.
Victims' groups had complained earlier in the week that Francis had neglected to address their plight when he congratulated bishops for their "courageous" and generous response to the scandal. Sunday's meeting took place a day after the pope celebrated Mass with Justin Rigali, the cardinal who was archbishop in Philadelphia when the archdiocese was accused of sheltering pedophiles.
The Vatican spokesman, the Rev. Federico Lombardi, said the pope met with the survivors for a half-hour at the San Carlo Borromeo seminary. He said the pope prayed with them, listened to their stories and expressed his closeness in their suffering and his "pain and shame" in the case of those abused by priests.
"He renewed his commitment and that of the church so that victims are heard and treated with justice, that the guilty are punished and that the crimes of abuse are fought with efficient prevention efforts in the church and society," Lombardi said in a statement. "The pope thanked the victims for their essential contribution to establish the truth and begin the path of healing."
Later Sunday, Francis was scheduled to visit a prison and celebrate a final Mass on U.S. soil on Philadelphia's grandest boulevard, the Benjamin Franklin Parkway.
Organizers said they expected 1 million people to turn out. But there were fears that the extraordinary security -- including airport-style bag searches, crowd-control cattle chutes and blocked-off streets -- would scare away many.
Roman Catholics from across the country and around the world began making the trek to the Mass hours ahead, crossing bridges on foot and packing subway cars.
At Curran-Fromhold Correctional Facility, Francis planned to visit with 100 inmates, including suspected killers, rapists and mobsters. He was expected to offer them words of hope, forgiveness and redemption.
"His mission is the marginalized, the forgotten," prison spokeswoman Shawn Hawes said. "From our understanding, he wants those who are in custody to know that they are not forgotten and they can be redeemed."
Prison ministry has been a hallmark of Francis' pontificate. He meets often with inmates and has washed prisoners' feet during pre-Easter rituals. He opposes the death penalty in all circumstances and has called for the abolition of life imprisonment and solitary confinement.
On Saturday night, Francis was cheered by tens of thousands at a music-and-prayer festival on the Parkway, waving to the crowd in his open-air popemobile. Performers included Aretha Franklin and Andrea Bocelli.
He called families a "factory of hope," even with their imperfections.
"Defend the family, because that's where our future will play out," he said.
Thomas Coorey, a dentist and father of four visiting Philadelphia from Sydney, called Francis "the most inspirational and amazing pope that could breathe life into this church of mine. And I'm so grateful to have a leader like him who's so humble and such a true servant of God."
It's been a common sentiment throughout the pope's visit to Washington, New York and Philadelphia.
"It's the wave. It's the smile," said Tom Hambrose, 52, of Haddon Heights, New Jersey, attending the Festival of Families on Saturday night. "It's what he's articulating, that the church needs to step forward and needs to change its thinking about things."
Associated Press writers Michael R. Sisak, Maryclaire Dale and Kathy Matheson contributed to this report.